Clamping platen movable

The equipment for thermal sealing usually comprises a press with at least one movable platen bar often there are two bars, which can be adjusted to give the clamping action that is required. The bars are resistance heated by means of a low-voltage heavy electric current the degree of heating is controlled automatically by a thermostat, and often it can be pre-set. 

The clamping debars (rods) can be used to support the fixed and movable platens on which the mold is attached. They serve as equally loaded tension support members of the clamp when the mold is closed. The open distance between tie rods through which the mold must fit and eject molded parts sets up the maximum outside dimensions of the mold that can be used. Different designs are used to meet different... 

The clamping unit consists of one fixed platen and one movable platen. One mold half each is installed on one of the platens. 

A conventional hydrauhc clamp (Fig. 5.61 ) has one large cylinder in the center of the movable platen with no mechanical advantage applied. Thus, hydrauhc fluid and pressure open and close the clamp. To move the clamp forward, hydraulic fluid is directed to a booster tube or cylinder and the prefill valve is opened. As the booster cylinder... 

In the injection molding machine shown in Figure 13, the clamp unit is on the left and the injection unit on the right. A mold is shown in position between the platens of the clamp unit with one half of the mold fastened to the fixed platen and the other to the movable platen. When the mold is opened, the movable platen moves away from the fixed platen and the molded part can be removed. After part ejection, the mold is closed in preparation for the next injection cycle. In contrast to extrusion, the screw in the injection imit rotates only during part of molding cycle. When the screw turns, it pumps melt forward. The rearward movement of the screw is controlled by the placement of a limit switch, which stops the hydraulic motor. The maximum length of reciprocation is approximately three screw diameters. The shot size is directly proportional to the amoimt of screw... 

Figure 7.2 Typical direct hydraulic clamp uniU A Actuating plunger, B removable spacer, C mold, D injection nozzle, E fixed platen, F movable platen, G tiebar, H cylinder base plate, I clamping cylinder.

Figure 7.3 Typical toggle clamp unit. A Movable platen, B fixed platen, C mold, D front link, E rear link, F actuating cylinder, G tiebar, H crosshead link.

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